UCLA

Introduction The United States has seen a rise in methamphetamine use disorders and methamphetamine-involved deaths. However, there is limited information on methamphetamine at the consumer level. We leverage data from a community-based drug checking program in Los Angeles to investigate the makeup of the retail illicit methamphetamine market and the extent methamphetamine plays a role as an adulterant in other drugs. Methods Participants accessing a community-based drug checking program provided samples of drug products and completed brief interviews in Los Angeles County, California, from 2023 to 2025. Samples underwent laboratory-based qualitative and quantitative mass spectrometry. We quantitated the presence and concentration of methamphetamine as well as all other identified substances among samples expected only to be methamphetamine and samples expected to be another substance (e.g., fentanyl, heroin) where methamphetamine was found as an adulterant/contaminant. Results Of N=2193 total samples, n=652 (29.7%) were methamphetamine-positive on DART-MS. In samples expected to contain methamphetamine, the mean purity was 78.2% (SD 24.0%; range <1% to ≈100%). As an unexpected component, the mean methamphetamine purity was 17.8% (SD 32.3%) and was mostly found in samples expected to be fentanyl, heroin, other amphetamines. Conclusions Consumers in Los Angeles seeking methamphetamine appear to frequently obtain high-purity samples that are rarely adulterated with other substances, although we observed a wide variation in concentration between samples. In contrast, drugs purchased without the expectation of containing methamphetamine had high prevalence of methamphetamine adulteration/contamination. Future research should expand methamphetamine surveillance techniques and investigate how variability in illicit markets may impact health outcomes.